With increasing development of scientific technologies, multimedia products and computers become essential in our daily lives. In the computer systems, peripheral input devices play important roles for communicating the computer systems and the users. The common peripheral input devices of the computer systems include for example mice, keyboards, microphones, or the like. When a mouse is held on the palm of a user's hand, the user may move the mouse to control movement of the cursor shown on the computer screen. As the cursor is moved, the motion trajectory of the mouse cursor is shown on the computer screen. Since mice are very easy-to-use and can comply with the usual practices of most users, mice are the most prevailing among these peripheral input devices.
Generally, during a document file or a web page is browsed by a user, if the document file or the web page is too large, the image frame shown on the computer screen need to be scrolled in a vertical direction and a horizontal direction, so that the whole contents can be browsed by the user. Since the wheel of a conventional mouse device permits for single axial rotation, the image frame shown on the computer screen can only be vertically scrolled. For performing the horizontal scrolling operation, the left click button of the mouse should be continuously pressed down while the mouse is moved in the horizontal direction. Since the single axial rotation of the mouse is unsatisfactory for the user to browse the document file or the web page, a tilt wheel mouse is developed for controlling horizontal scroll movement of the image shown on the computer screen.
FIG. 1 is a schematic perspective view illustrating the outward appearance of a conventional wheel mouse. As shown in FIG. 1, the tilt wheel mouse 1 comprises a casing 10 and a wheel 11. The casing 10 has an opening 101. Through the opening 101, the wheel 11 is protruded from an outer surface of the casing 10, so that the wheel 11 can be manipulated by a user. By rotating the wheel 11 forwardly (in the direction D1) or backwardly (in the direction D2), the tilt wheel mouse 1 generates a first control signal. According to the first control signal, the computer executes a first command of vertically scrolling the image frame shown on the computer screen for example. By tilting the wheel 11 toward the left side (in the direction D3) or the right side (in the direction D4), the tilt wheel mouse 1 generates a second control signal. According to the second control signal, the computer executes a second command of horizontally scrolling the image frame shown on the computer screen for example.
Although the wheel 11 of the conventional tilt wheel mouse can be rotated forwardly (in the direction D1) or backwardly (in the direction D2) and tilted toward the left side (in the direction D3) or the right side (in the direction D4), there are still some drawbacks. For example, during the wheel 11 is tilted toward the left side or the right side by the user's finger, the wheel 11 may be simultaneously rotated forwardly or backwardly because the depressing force resulting from the user's finger is improperly exerted on the wheel 11. Under this circumstance, the first control signal and the second control signal are accommodated by the computer at the same time. Since the computer fails to judge which command should be executed, the tilt wheel mouse 1 is readily suffered from an erroneous operation. This erroneous operation may bring about considerable trouble to the user.
Nowadays, as the professional computer software becomes more and more diverse, its functionality is increased but the operations of the software are more complicated. Since the wheel of the conventional tilt wheel mouse is permitted to be rotated forwardly and backwardly or tilted toward the left side and the right side, the functions provided by the conventional tilt wheel mouse fail to meet the requirements of most users. Therefore, the conventional tilt wheel mouse needs to be further improved.